JERRY'S
MODEL RAILROAD PRINTED CIRCUIT BOARDS
MRR PCB
5138 Atchinson Drive SE
Olympia, WA 98513-4529
Phone: (360)456-0572
Model Railroad Printed Circuit Boards
R-4-2 RELAY PRINTED CIRCUIT BOARD
The MRR PCB R-4-2 © relay card offers flexible options for four (4) DPDT Relays. These relays can control or switch very heavy loads up to eight (8) amps.
By installing various jumpers, the card may be used as:
1. One (1), two (2), three (3) or Four (4) DPDT Relays
2. One (1) 4PDT Relays and two (2) DPDT Relays
3. One (1) 6PDT Relay and (1) DPDT Relay
4. One (1) 8PDT Relay
5. Two (2) 4PDT Relays
When the MRR PCB R-4-2 relays are turned on and off, the relay coil may generates a large back EMF, resisting the rapid change in voltage. The Card has the option to add a diode to short out the back EMF and protect the circuit. A small silicon switching diode should be sufficient.
BE SURE to use the proper relay for the DC power supply voltage that you are using to power your accessories; note that some relays are rated for 5 volts DC, 10 volts DC or 24 volts DC.
Why a relay? I know there are some new devices out there to control crossing gates, dwarf signals, signal bridges, etc., but I feel the good old fashioned relays do a better job. Plus Relays still have many uses.
Some of their uses are:
1. A relay can cut off track power to prevent a locomotive from moving while the turntable is running...
2. A relay can be used for Power routing turnout points, Tortoise switch machine contacts are rated at 1 amp and can be damaged by Large motive power consists or shorts.
3. A relay can be used to switch power to a simple signaling system’s lights.
4. A relay can solve reversing problems when wiring in wyes, loops, reversing loops and turntables.
© Jerry F. Barnes… 19 January 1997.
R-4-2 Schematic Drawing
R-4-2 Relay Printed Circuit Board
ORDER FORM
Started Counting: 07 July 2002
Last Date Revised: 22 October 2002
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